1. Field of the Invention
The present invention relates to resistive paste which contains a conductive component prepared from iron oxide, ruthenium oxide, lead oxide and zinc oxide.
2. Description of the Prior Art
Examples of conventional resistive paste materials containing conductive components of metal oxides are Bi.sub.2 O.sub.3 -RuO.sub.2 paste which is disclosed in Japanese Patent Publication No. 27871/1976, Pb.sub.3 O.sub.4 -RuO.sub.2 paste which is disclosed in Japanese Patent Publication No. 28162/1980, and Fe.sub.3 O.sub.4 -RuO.sub.2 -Pb.sub.3 O.sub.4 paste which is disclosed in Japanese Patent Laying-Open No. 208201/1986.
Such well-known paste is applied by screen printing onto an insulating substrate of alumina, for example, and fired in the air, to provide a resistor for a semi-fixed resistor.
However, such a resistor is so inferior in slidability that sliding noise, i.e., contact resistance variation (C.R.V.) is at least 3 percent when a slider is slid on this resistor.
As to the components of the aforementioned conventional resistive paste materials, the Bi.sub.2 O.sub.3 -RuO.sub.2 paste contains Bi and Ru in the mole ratio 4:5 to 4:8 while the Pb.sub.3 O.sub.4 -RuO.sub.2 paste contains Pb.sub.3 O.sub.4 and RuO.sub.2 in the mole ratio 1:1 to 2:1. The conventional resistive paste materials thus contain large amounts of high-priced RuO.sub.2 are inevitably high in cost.